In prior art bias ply tires, the opposed angles of the reinforcement cords in adjacent carcass plies in the tire caused the carcass plies to work against each other, and this construction caused the bias ply tire to act as a unit. That is, stresses encountered by the tire while rolling on a vehicle were distributed throughout the tire. The breaker package in the tire provided a constant to stiffen the tire and reduce its deformation, and provided a base for a flattened tread against the road.
With the advent of the radial ply tire, the high angles of the reinforcement cords in the carcass plies, relative to the equatorial plane (EP) of the tire, reduced the interaction between the carcass plies and increased the flexibility of the sidewalls. The increased flexibility in the sidewalls reduced stresses on the crown and tread area of the tire since most of the energy absorbed by the tire while running on a vehicle was absorbed by the sidewalls.
Moriyama in U.S. Pat. No. 5,746,860, teaches a low-section profile pneumatic radial tire which is manufactured by using a green tire built in a first and a second building steps, wherein an uncured inner sidewall rubber segment and an uncured outer sidewall rubber segment are separately provided to correspond to an inner portion and an outer portion, and parted from each sidewall rubber of a tire, after vulcanization. The components are provided in a radial direction in the tire, providing a parting face located on an outer surface of the sidewall rubber which is not more than one half of a section height of the tire. The uncured inner sidewall rubber segment is attached in the first building step, and the uncured outer sidewall rubber segment is attached at the second building step. This construction is said to provide a tire which has excellent resistance to cracking in the sidewall portion without degrading tire performance.
Morel, in International Publication WO 99/42307, teaches a tire with a body ply reinforcement (1), a top ply reinforcement (3), and a tire tread (4) joined to two tire beads via two sidewalls (5). The axially outer edges of the tire tread are folded down over the radially outer ends of the sidewalks. A secular joint (J) between the tread and the sidewall is positioned such that its radius (R C) on the tire (P) axially outer wall ranges between 0.9 RS plus 0.1 RB and 0.8 RS plus 0.2 RB, and between RSS and 0.9 RSS plus 0.1 RB, where RS is the tire tread equatorial radius and RSS is the body ply mean line equatorial radius, and RB is the tire bead seat.
Continental Tire has published advertising that describes a “flat belt concept”. A tire made using the “flat belt concept” is said to have a flatter contour which increases the contact area on the road's surface, and reduces the flexing of the tire. This is said to result in slow and even wear.
Scarlett, in Tire Technology International, September, 1998, pp. 15-17, and Drieux et al., in U.S. Pat. No. 5,785,781 teach a tire with an axially outer bead tip that is said to divorce the bead from the sidewall of the tire, the bead acting as a fulcrum to convert outward tension for tire retention.
U.S. Pat. No. 4,124,679 to DeWitt teaches a method of building a tire with unequal bead diameters where the two sidewalls of the tire have different profiles in the mold.
U.S. Pat. No. 4,147,751 to Duderstadt et al., teaches a method of making a pneumatic tire wherein the tire is cured in a mold with a curved configuration having the same tread radius in the center, and an increased tread radius at the margins of the tread.
U.S. Pat. No. 4,815,511 teaches a tire made using multiple radii in the mold shape.
It is an object of the invention to provide a new concept in tire design, which will improve the overall wear, handling, rolling resistance and traction properties of a tire.
Other objects of the invention will be apparent from the following description and claims.